The condition of a tire is directly related to the safety of vehicle passengers, and usually, the timing for replacement and the condition of a tire are determined based on the abrasion state of the tread formed on the tire.
However, although the abrasion state of the tread may serve as an indicator showing the condition of a tire, the tread abrasion state is somewhat insufficient as information indicating the general condition of a tire. There is a variety of information that should be monitored for the vehicle safety, such as the air pressure inside the tire, temperature, speed of rotation, and pressure, as well as the angle formed by the tire and the axis during driving, and these information pieces need to be collected and understood in real time for the safety of passengers.
Accordingly, there have been attempts to mount sensors on the tires for motor vehicles and aircraft; however, it is not easy to install a sensor inside a tire that rotates at a high speed, and there has been a problem that an installed sensor is easily detached due to the friction heat and vibration generated when the tire rotates. In some aircraft tires, it was attempted to solve this problem by disposing a thin RFID sensor between the outer circumference and the inner liner of a tire; however, it was not easy to insert a sensor in the middle of vulcanization of the tire, and there was a risk of the sensor being damaged due to exposure to a high temperature.
In this regard, Japanese Patent Application Laid-Open (JP-A) No. 2000-168321 suggested “a method for preparing a pneumatic tire for binding an electronic monitor device”, by which separation of a sensor from an inner liner of a tire is prevented by vulcanizing a patch into the inner liner and inserting a sensor therein. However, in JP-A No. 2000-168321, the patch is formed to have a large thickness, so that the pressure of the bladder may be exerted locally non-uniformly on the inner liner during the vulcanization process, and in this case, there is a risk that uneven wear may occur in the tire. Furthermore, there is a possibility that the space for inserting the sensor may be formed to be excessively large so that the sensor may be shaken therein, and this means that the sensor may be detached and removed. Furthermore, the sensor is attached to the bead side so that the sensor may be damaged at the time of installing or uninstalling the tire, and the sensor patch is composed of various parts such as a cover, an unvulcanized rubber layer and paper and has a complicated structure. Also, since heat transfer is not easily achieved so that vulcanization may take a long time, or the temperature may increase high, causing deterioration of the energy efficiency.